Sensing mechanism for impression cylinders

ABSTRACT

An impression cylinder of a printing press is provided with a rotatable shaft journalled parallel to its axis. The shaft has at least two feelers mounted thereon which are resiliently urged upward out of the cylinder, so as to contact the sheet fed to the cylinder. The shaft and the feelers are provided with cooperating abutment means which cause the feelers to rotate the shaft in one direction. The shaft is provided with lever means at one of its exterior ends which cooperate with the tripping-off control means. The shaft is provided with spring means which rotates the shaft counter to the action of the feeler spring. The feeler spring has a force greater than that of the shaft spring so that in the absence of the effect of a paper sheet, the shaft is rotated to cause the lever means to activate the tripping-off mechanism but to be ineffective when a sheet is properly aligned on the cylinder and properly sensed.

limited States Patent [191 .1 urny et a1.

[ 4] SENSING MECHANISM FOR IMPRESSION CYLINDERS [75] Inventors: Josef Jurny, Sebranice; Vaclav Sedlak, Jedovnice, both of Czechoslovakia [73] Assignee: Adamovske Strojurny, narodni podnik, Adamov, Czechoslovakia 22 Filed: May 17, 1972 [21] Appl. No.: 254,051

[30] Foreign Application Priority Data May 20, 1971 Czechoslovakia 3667/71 [52] US. Cl 101/232, 101/233, 101/246, 101/247 [51] Int. Cl B4lf 13/24 [58] Field of Search 101/247, 234, 235, 101/236, 237, 49, 232, 233; 340/259;

[451 Ja1n.1,1974

Primary Examiner-Robert E. Bagwill Assistant ExaminerWilliam Pieprz AttorneyMurray Schaffer et a1.

[57] ABSTRACT An impression cylinder of a printing press is provided with a rotatable shaft journalled parallel to its axis. The shaft has at least two feelers mounted thereon which are resiliently urged upward out of the cylinder, so as to contact the sheet fed to the cylinder. The shaft and the feelers are provided with cooperating abutment means which cause the feelers to rotate the shaft in one direction. The shaft is provided with lever means at one of its exterior ends which cooperate with the tripping-off control means. The shaft is provided with spring means which rotates the shaft counter to the action of the feeler spring. The feeler spring has a force greater than that of the shaft spring so that in the absence of the effect of a paper sheet, the shaft is rotated to cause the lever means to activate the tripping-off mechanism but to be ineffective when a sheet is properly aligned on the cylinder and properly sensed.

5 Claims, 5 Drawing Figures PATENTED JAN H974 SH'LU 1 0F 2 SENSING MECHANISM FOR IMPRESSION CYLINDERS BACKGROUND OF INVENTION The present invention relates to apparatus for tripping-off the print rollers in an offset printing machine and in particular to apparatus for sensing the absence or faulty feeding of paper sheets on the impression cylinder and in response thereto control the tripping-off process.

Mechanical or electrical mechanisms for the control of the presence of a paper sheet are known in which a mechanical feeler actually guides and controls the presence of the paper sheet either during its transportation and before it is seized by the grippers of the impression cylinder, or after the paper is seized by the grippers. A disadvantage of these devices is that, if a failure occurs just prior to the seizing of the paper sheet by the grippers, the feeler dos not respond and does not give, in sufficient time, the necessary signal for tripping-off the printing cylinders from printing pressure. Such mechanisms do not carry out a complete service in that they fail at the most crucial time of the print cycle.

Feeler devices which are arranged in the interior of the impression cylinder are known which are provided with mechanical feelers which are rigidly mounted on a shaft rotatably arranged in the impression cylinder. A lever having rollers, is rigidly mounted on one end of said shaft, one of said rollers following the functional surface of an outer or an inner cam to control the movement of the feeler elements and the second roller responds, in the case of absence of a paper sheet in the grippers of the impression cylinder, to give an impulse for the tripping-off the printing cylinders from printing pressure.

The above devices have other disadvantages in the event of the feeding of a skewed paper sheet, a part of the sheets edge which is not seized by the grippers becomes folded over. The feelers of the known devices do not, however, give an impulse for the tripping-off the printing cylinders. As a result the folded paper causes an excess of pressure on the surface of the offset blanket and so the blanket is quickly damaged. The offset blanket then must be frequently changed, particularly when a high quality print is required. The faulty seized paper sheet cannot be transported the grippers and as the printing cylinders are not tripped 011' from pressure contact, while the feeding device continues to feed further paper sheets which begin to crowd and pile up in the printing mechanism. Damage of the printing machine can easily occur unless the machine is immediately, manually stopped by the operator.

It is an object of the present invention to provide a device for insuring proper paper feed to the impression cylinder and to overcome the disadvantages and de fects of the prior art.

It is a further object of the present invention to provide apparatus for sensing the faulty feeding of paper sheets to the impression cylinder and for providing an immediate response and signal for tripping-off the print rollers.

It is a further object of the present invention to provide apparatus of the type descrived in which the feelers are more sensitive and arranged to sense not only the absence of a sheet, butits skew and folded-over corners. I

These objects, others and numerous advantages will be seen from the following disclosure.

SUMMARY OF INVENTION 0 the sheet. The shaft and the feelers are provided with cooperating abutment means which cause the feelers to rotate the shaft in one direction. The shaft is provided with lever means at one of its exterior ends which cooperate with the tripping-off control means. The shaft is provided with spring means which rotates the shaft counter to the action of the feeler spring. The feeler spring has a force greater than that of the shaft spring so that in the absence of the effect of a paper sheet, the shaft is rotated to cause the lever means to activate the tripping-off mechanism but to be ineffective when a sheet is properly aligned on the cylinder and properly sensed.

Preferably, a plurality of feelers are provided, each one individually capable of overcoming the shaft spring and activating the tripping-off mechanism.

It is also preferable to employ a feeler in which the abutment means is fixed between a hub yoke to prevent axial movement and has screw adjustment means to vary the degree of pivoting. A compression spring is used for the feeler spring while a torsion spring is used for the shaft spring.

Full details of the present invention are set forth in the following description and shown in the drawings.

BRIEF DESCRIPTION OF DRAWINGS In the drawings:

FIG. 1 is a fragmentary plan view of an impression cylinder in which the present invention is embodied,

FIG. 2 is a sectional view taken in the plane A-A of FIG. I, with a sheet of paper on the cylinder,

FIG. 3 is a view as seen in the direction of arrow P of FIG. 1, with a paper sheet,

FIG. 4 is a view similar to FIG. 3 without the paper sheet, and

FIG. 5 is a view similar to FIG. 4 without a paper sheet.

The drawings show only so much of a printing machine, such as an offset printing machine, as is necessary to understand the present invention. The structure and function of an impression cylinder, and its operative relation to the remainder of the press are so well known as not to be required to be described in detail, herein.

, DESCRIPTION OF INVENTION As seen in FIG. 1, a pair of feelers l are freely mounted about a shaft 2. The feelers 1 are shaped to sense the pre-sence of paper sheets such as 19, in or entering into the grippers 20 on the surface of the impression cylinder 3. The shaft 2 is journalled in the impression cylinder 3 by a radial bearing 4 at each end. The radial bearings 4 are fixed in the frontal ends of the cylinder 3 adjacent the surface and parallel to the axis of rotation of the impression cylinder 3. The feelers] are elongated members having their front ends adjacent the grippers and aligned therewith to grip the sheet. The feelers have a yoke or split hub 25 at its rear end by which they are attached to the shaft 2. Fasteners 5 screwed into the shaft fix an abutment member 6 between the walls of the yoke of the feelers l. The abutment member 6 permits the feeler 1 to have a degree of pivotal movement but little, if any, axial movement relative to the shaft 2. Each feeler l is urged upwardly by a compression spring 7 located in front of the shaft 2 and seated at its lower end on a support 23 fixed to the internal web of the impression cylinder 3. A stop screw 8, secured by a pair of nuts 9 is adjustably mounted in the feeler l to bear with its front end against the abutment member 6. Adjustment of the stop screw 8 against the abutment member 6 selectively regulates the degree of pivotal movement of the feeler 1 relative to the abutment member created by the bias of spring 7. In this manner, the upward bias of the feelers I tend to pivot the shaft 2 in a counter-clockwise manner.

A screw 10 fixes the hub of a two armed lever 11 at one of the ends of the shaft 2. The lever 11 has afirst portion on which a roller 12 is secured. The roller 12 lies in a plane parallel to frontal ends of the impression cylinder and is mounted at the end of an axle 14 having an eccentric cross-section. The axle 14 lies generally parallel to the axis of the cylinder. The lever 11 has a second portion on which a roller 13 extends laterally in a plane parallel to the axis of the impression cylinder and is secured about an axle 18 perpendicular to the axis of the cylinder. The roller 12 is mounted at the end of an extending eccentric axle 14 which is adjusted by rotation so that the roller 12 bears against the functional or contoured edge of cam 15. The cam 15 is secured axially to a flange 16 fixed to a side wall 17 of the printing machine frame. The roller 13 is mounted on an axle bearing 18 and is selectively adapted, (i.e., in the absence of a paper sheet 19) to engage a projecting sloping cam surface 21 fixed at the end of a horizontally freely movable rod 24 located in a sleeve fixed in the wall 17. The position of the roller 13 radially about the shaft 2 is determined by adjustment of the axle 14 which, of course, determines the position of lever 11 when in contact with the cam 15 as seen in FIG. 5. The rod 24 is provided with a spring, resiliently biasing the inclined cam surface 21 in proper position. The rod 24 is connected to suitable control elements such as a switch, relay or other means for controlling the tripping-off of the printing rollers.

The cam 15 is contoured so that when the roller 12 is urged against it, the lever 11 is pivoted by a rise in the cam to cause the roller 13 to engage the slanted cam 21. This creates a tripping-off signal at the proper moment in the printing cycle so that the cycle is not effected by the normal absence of a sheet between printing intervals, for example.

A torsion spring 22 is mounted about the shaft 2 and is fixed at one end in the frontal end of the impression cylinder and at its other end in the hub of the lever 11. The torsion spring 22 acts in the opposite direction of the spring 7 to urge the shaft 2 in a clockwise direction so that the abutment element 6 is urged to bear against the screws 8. ln the non-working condition or in the absence of a paper sheet on the cylinder, the spring 7 pivots the feelers l upwardly, as seen in H0. 4. The force of each one of the compression springs is selected to be greater than the force of the torsion spring 22, so that the upward movement of either one of the feelers 1 causes the shaft 2 to move counter-clockwise, swinging the lever 11 also counter-clockwise so that the roller 12 is urged to bear against the cam 15 and the roller 13 is in a position to engage the slanted cam surface 21.

In operating the press, as soon as a paper sheet 19 is properly fed and is seized by the grippers 20, the feelers 1 are depressed allowing the torsion spring 22 to urge the shaft 2 clockwise until the abutment member engages the screw 8. The lever 11 is also pivoted clockwise lifting the roller 12 from the cam 15 and moving the roller 13 out of the path of the slanted cam 21. In this manner, the cam 21 does not effect the tripping-off operation of the printing rollers and the press continues its operation with the printing cylinders under pressure, and the sheets normally printed.

On the other hand, as soon as one or both of the feelers do not sense a sheet, or sense only a portion of the sheet, or the absence of the whole or a major part of the sheet in the vicinity of the feeler urge the feelers 1 upwardly, causing the screw 8 to hit the abutment member 6, pivot the shaft 2 so that the roller 12 engages the cam and causes it to actuate the roller 13 at the proper moment to engage the slanted cam 21 and thereby cause a tripping-off of the print rollers. The tripping-off operation also effects the cessation of paper feed by a conventional mechanism.

The advantages of the present invention reside in the construction wherein a plurality of pivotal feelers 1 may be located on the common shaft 2. While two are shown, more may obviously be used, each being biased by a spring 7 of sufficient strength to individually and separately overcome the counter bias on the torsion spring 22. Thus, not only can the absence of an entire sheet be sensed but also faulty, torn sheets, folded sheets and other imperfections in sheet or feeding process.

In addition to the sensing of no sheet, folded sheet and skewed sheet, the feelers sense when a sheet is not properly engaged by the grippers. This occurs because of the arrangement of the feelers to cooperate with the grippers to engage the sheet. Piled up sheets cannot easily occur, as tripping-off and cessation of feed will be almost instantaneously, and no more than one revolution of the cylinder.

A further advantage arises from the fact the embodiments for carrying out the invention are simple, therefore, requiring very little structural or functional change in the remaining portions of the press.

Various changes and modifications can be made. Accordingly, it is intended that the present disclosure be taken as illustrative only and not limiting of its scope.

What is claimed:

1. Apparatus for controlling the tripping-off of printing cylinders in response to the absence of a sheet or the presence of an improperly aligned paper sheet on the impression cylinder of a printing press, comprising an impression cylinder having a gap in its circumference, a rotatable shaft journalled within said cylinder parallel to the axis thereof, a lever mounted at one end of said shaft externally of said cylinder, said lever being movable on rotation of said shaft into and out of engagement with control means for effecting tripping-off, first spring means comprising a torsion spring mounted about said shaft having one end secured to the impression cylinder and the other end to the lever for urging said shaft in a first rotary direction to cause said lever to disengage from said control means, at least two sheet feelers pivotally mounted on said shaft and extending through said gap in said cylinder, abutment means for limiting the pivoting of each feeler, second spring means acting on each of said feeler to urge said feelers outwardly of said cylinder and to engage said abutment means to cause said shaft to rotate in a direction opposite to said first direction, each said second spring means having a force greater than said first spring means to normally cause said shaft to be biased in said opposite direction to maintain said lever in engagement with said control means, the force of each said second spring means being overcome by contact with a sheet on the surface of said cylinder, permitting said first spring means to rotate said shaft in said first direction to disengage said lever from said control means.

2. The apparatus according to claim 1, wherein said control means comprises a fixed edge cam, and a movable rod having an inclined surface, said rod being adapted to initiate the tripping-off, said lever having a roller adpated to engage said cam when said shaft is rotated in said opposite direction, and a second roller aligned with said rod surface, said cam edge having a contour to cause said second roller to engage said rod surface when the fixed edge cam has rotated to a predetermined position.

.3. The apparatus according to claim 1 wherein each feeler is freely mounted about said shaft by a yoke, said abutment member being secured to said shaft within said yoke, said feeler including an adjustable screw adapted to bear against said abutment member.

4. The apparatus according to claim 3 wherein the second spring means comprises a compression spring supported by the cylinder and bearing against said feeler.

5. Apparatus for controlling the tripping-off of printing cylinders in response to the absence a sheet of or the presence of an improperly aligned paper sheet on the impression cylinder of a printing press, comprising an impression cylinder having a gap in its circumference and a plurality of gripper means extending along the edge of said gap to grasp a sheet placed on the surface of the cylinder, a rotatable shaft journalled within said cylinder parallel to the axis thereof, a lever mounted at one end of said shaft externally of said cylinder, said lever being movable on rotation of said shaft into and out of engagement with control means for effecting tripping-off, first spring means for urging said shaft in a first rotary direction to cause said lever to disengage from said control means, at least two sheet feelers pivotally mounted on said shaft, said feelers being spaced along said shaft and extending through said gap in said cylinder in alignment with said gripper means to be engageable by a sheet when grasped by said gripper means, abutment means for limiting the pivoting of each feeler, second spring means acting on each of said feeler to urge said feelers outwardly of said cylinder and to engage said abutment means to cause said shaft to rotate in a direction opposite to said first direction, each said second spring means having a force greater than said first spring means to normally cause said shaft to be biased in said opposite direction to maintain said lever in engagement with said control means, the force of each second spring means being overcome by contact of the associated feeler with a sheet grasped by said grippers, said first spring means thus being permitted to rotate said shaft in said first direction to disengage said lever from said control means only on contact of all feelers with said sheet. 

1. Apparatus for controlling the tripping-off of printing cylinders in response to the absence of a sheet or the presence of an improperly aligned paper sheet on the impression cylinder of a printing press, comprising an impression cylinder having a gap in its circumference, a rotatable shaft journalled within said cylinder parallel to the axis thereof, a lever mounted at one end of said shaft externally of said cylinder, said lever being movable on rotation of said shaft into and out of engagement with control means for effecting tripping-off, first spring means comprising a torsion spring mounted about said shaft having one end secured to the impression cylinder and the other end to the lever for urging said shaft in a first rotary direction to cause said lever to disengage from said control means, at least two sheet feelers pivotally mounted on said shaft and extending through said gap in said cylinder, abutment means for limiting the pivoting of each feeler, second spring means acting on each of said feeler to urge said feelers outwardly of said cylinder and to engage said abutment means to cause said shaft to rotate in a direction opposite to said first direction, each said second spring means having a force greater than said first spring means to normally cause said shaft to be biased in said opposite direction to maintain said lever in engagement with said control means, the force of each said second spring means being overcome by contact with a sheet on the surface of said cylinder, permitting said first spring means to rotate said shaft in said first direction to disengage said lever from said control means.
 2. The apparatus according to claim 1, wherein said control means comprises a fixed edge cam, and a movable rod having an inclined surface, said rod being adapted to initiate the tripping-off, said lever having a roller adpated to engage said cam when said shaft is rotated in said opposite direction, and a second roller aligned with said rod surface, said cam edge having a contour to cause said second roller to engage said rod surface when the fixed edge cam has rotated to a predetermined position.
 3. The apparatus according to claim 1 wherein each feeler is freely mounted about said shaft by a yoke, said abutment member being secured to said shaft within said yoke, said feeler including an adjustable screw adapted to bear against said abutment member.
 4. The apparatus according to claim 3 wherein the second spring means comprises a compression spring supported by the cylinder and bearing against said feeler.
 5. Apparatus for controlling the tripping-off of printing cylinders in response to the absence a sheet of or the presence of an improperly aligned paper sheet on the impression cylinder of a printing press, comprising an impression cylinder having a gap in its circumference and a plurality of gripper means extending along the edge of said gap to grasp a sheet placed on the surface of the cylinder, a rotatable shaft journalled within said cylinder parallel to the axis thereof, a lever mounted at one end of said shaft externally of said cylinder, said lever being movable on rotation of said shaft into and out of engagement with control means for effecting tripping-off, first spring means for urging said shaft in a first rotary direction to cause said lever to disengage from said control means, at least two sheet feelers pivotally mounted on said shaft, said feelers being spaced along said shaft and extending through said gap in said cylinder in alignment with said gripper means to be engageable by a sheet when grasped by said gripper means, abutment means for limiting the pivoting of each feeler, second spring means acting on each of said feeler to urge said feelers outwardly of said cylinder and to engage said abutment means to cause said shaft to rotate in a direction opposite to said first direction, each said second spring means having a force greater than said first spring means to normally cause said shaft to be biased in said opposite direction to maintain said lever in engagement with said control means, the force of each second spring means being overcome by contact of the associated feeler with a sheet grasped by said grippers, said first spring means thus being permitted to rotate said shaft in said first direction to disengage said lever from said control means only on contact of all feelers with said sheet. 